He probably wasn’t arrested. It sounds like the police handcuffed him while checking whether he was indeed alone and then asked about what he was doing at his computer. After he explained, they asked him to turn off the stream, at which point I would assume he was freed again.
I assume they went on to explain the situation and then questioned him. If there is no evidence of any crime, they will just take his personals so they can contact him on any development. He is the victim of a crime after all.